Silane crosslinked polyethylene cable material as insulation material for low-voltage power cables has been widely used in China's wire and cable industry. Compared with peroxide cross-linking and irradiation cross-linking, this material has the advantages of simple manufacturing equipment, convenient operation and low comprehensive cost. It has become the leading insulating material for low-voltage cross-linked cables.

Principle of Silane Crosslinking Cable Material

There are two main processes in the preparation of silane crosslinked polyethylene: grafting and crosslinking. In the process of grafting, free radicals were produced by the free initiator and pyrolysis free radicals, which lost H atom on tertiary carbon atom. The free radicals reacted with vinylsilane - CH = CH2 group to form a grafted polymer containing trioxysilyl group.
During the crosslinking process, the grafted polymer was hydrolyzed to silanol under the action of water, and the Si-O-Si bond was formed by the condensation of-OH with the adjacent Si-O-H group, which resulted in the cross-linking of polymer macromolecules.

Principle of Silane Crosslinking Cable Material


Silane Crosslinked Cable Material and Its Cable Production Mode
As you know, the production of silane cross-linked cable materials and their cables can be divided into two steps and one step. The difference between two-step method and one-step method is where the silane grafting process takes place. The grafting process is carried out in two-step method at the cable material manufacturer and in one-step method at the cable manufacturer.
At present, the two-step silane crosslinked polyethylene insulation material with the largest market share in China consists of so-called A and B materials. A material is Polyethylene Grafted with silane and B material is catalyst master material. Its weight ratio is generally A:B = 95:5. A material and B material are made from cable material factory and sold to cable factory before they are used. After mixing with B material in proportion, the cable insulation core can be extruded in ordinary extruder, and then the insulation layer can be crosslinked in warm water or steam.
There is another kind of two-step silane crosslinked polyethylene insulation material. The production mode of material A is different. It is to introduce vinyl silane into the synthesis of polyethylene to directly obtain polyethylene containing silane branched chains. This method is essentially the production technology of resin, which must be completed by large petrochemical enterprises.
Material A of LINKLON silane material, which first entered China, belongs to this type. At present, DOW and BOREALIS silane materials are also of this type. There are no such products in domestic petrochemical enterprises.
There are also two types of one-step method. The traditional one-step method is to put all kinds of raw materials into a specially designed extruder to complete the grafting and extrusion of cable insulation cores by a special precision metering system according to the proportion of ingredients. In this process, there is no need for granulation, no need for the participation of cable material factories, and the cable factories are responsible for the grafting and extrusion of cable insulation cores. Do it alone. The production equipment and formulation technology of this kind of one-step silane cross-linked cable are mostly imported from abroad, which is expensive.
Another kind of one-step silane cross-linked polyethylene insulating material is produced by cable material manufacturer. It is a special method to mix all raw materials according to the proportion of formula. It is sold after packaging. There is no material A and B. The cable factory can directly complete the grafting and extrusion of cable insulating core at the same time in one step in the extruder. The unique feature of this method is that the silane grafting process can be completed in the ordinary PVC extruder without the expensive special extruder, and the two-step method of mixing material A and material B before extrusion is omitted.
There are two main processes in the preparation of silane crosslinked polyethylene: grafting and crosslinking. In the process of grafting, free radicals were produced by the free initiator and pyrolysis free radicals, which lost H atom on tertiary carbon atom. The free radicals reacted with vinylsilane - CH = CH2 group to form a grafted polymer containing trioxysilyl group.
During the crosslinking process, the grafted polymer was hydrolyzed to silanol under the action of water, and the Si-O-Si bond was formed by the condensation of-OH with the adjacent Si-O-H group, which resulted in the cross-linking of polymer macromolecules.